Solid waste incinerator

ABSTRACT

An incinerator for use in the kitchen with a heated air supply recirculating through an airtight combustion chamber in the absence of make-up air whereby during te initial stage of the operating cycle there is an oxygen starved condition to control combustion, vaporize the moisture and other volatiles and prevent backfires. Later in the cycle a supply of primary air is admitted to the combustion chamber. A blower is associated with the combustion chamber to recirculate a blast of air within the combustion chamber as well as to exhaust a portion of the air from the chamber. A fly ash separator is located downstream of this exhaust. A main heater means external of the combustion chamber is downstream of the fly ash separator, and it removes the smoke and odors and returns much of the heated air to the combustion chamber to complete the recirculation circuit and cause ignition of the solid combustibles. A portion of the heated air from the main heater means is fed to an afterburner wherein secondary air is admitted for replenishing the oxygen and completing the combustion of any volatiles that might remain in the exhaust gases, and then the gases are treated in a flame-box with a supply of tertiary air before the gases are returned to the atmosphere.

nite'd States Patent [191 Primary Examiner-Meyer Perlin Assistant ExaminerRonald C. Capossela Attorney-Richard L. Caslin ABSTRACT An incinerator for use in the kitchen with a heated air SECONDARY uR llllllllllllllllllllli an PRlMARV I 77 NR llllllllllllllllllllll I L iCOMBUSTlON I CHAMBER supply recirculating through an airtight combustion chamber in the absence of make-up air whereby during te initial stage of the operating cycle there is an oxygen starved condition to control combustion, vaporize the moisture and other volatiles and prevent backfires. Later in the cycle a supply of primary air is admitted to the combustion chamber. A blower is associated with the combustion chamber to recirculate a blast of air within the combustion chamber as well as to exhaust a portion of the air from the chamber. A fly ash separator is located downstream of this exhaust. A main heater means external of the combustion chamber is downstream of the fly ash separator, and it removes the smoke and odors and returns much of the heated air to the combustion chamber to complete the recirculation circuit and cause ignition of the solid combustibles. A portion of the heated air from the main heater means is fed to an afterburner wherein secondary air is admitted for replenishing the oxygen and completing the combustion of any volatiles that might remain in the exhaust gases, and then the gases are treated in a flamebox with a supply of tertiary air before the gases are returned to the atmosphere.

15 Claims, QDrawing Figures Box BURNER PATENTED J1|l3 samsun IZO FIGS

SOLID WASTE INCINERATOR BACKGROUND OF THE INVENTION The present invention relates to the art of solid waste incinerators in general, and particularly to a domestic incinerator which would be installed in the kitchen and would easily consume the amount of solid combustibles which accumulate in the average-size household. There is an evergrowing trend to use more prepackaged and prepared foods, disposable consumer items and reading material, and the disposal of this household waste and trash has become a major problem to the average family. The waste collection agencies are severely overloaded in coping with the growing household trash accumulation, as well as grass clippings, leaves and shrubbery trimmings that accumulate in the yard.

At the same time, air and water pollution are serious national problems. Together, waste disposal and environmental pollution present a dual problem that to date has defied adequate solutions. Over the years, most solid waste has been burned in municipal incinerators or used for land fill. Each method, however, contributes to pollution. The usual alternative to incineration, that is land fill, also faces increasingly severe limitations. Some major metropolitan areas are running out of space in which to dump solid waste. An estimated two-thirds of the cost of waste disposal is its collection. As labor costs increase and per capita generation of waste increases, these costs are due to increase. Many local building codes require Class A flues for domestic incinerators, and this has been a deterrent to the growth rate of such incinerators. Today, the concern over air pollution also is an additional limiting factor. In working toward a solution to the total problem of solid waste disposal, domenstic incinerators have so far played a minor role. Admittedly, a domestic incinerator can only handle solid waste combustibles like paper, cardboard and cellulose materials in general, plastics, food waste and the like, and not such things as glass, metal cans, aerosol cans, liquid volatiles, and the like, which should be disposed of by some other method. If the option of on-site incineration is eliminated by governmental restrictions, future costs of waste disposal would rise even higher. It behooves the appliance industry to perfect a practical domestic incinerator that does not contribute to existing air pollution problems.

In a typical metropolitan area, residential waste accounts for almost forty per cent of all tonnage generated. It is collected either by municipal collecting agencies or by private trash collectors. The basic problem in collecting and disposing of solid waste appears to be one of reducing volume without contributing to air and water pollution, and retaining the value of the land into which the residue is dumped. The use of domestic trash compactors installed in or near the kitchen is also growing in acceptance as an aid to the trash collection process. The food waste disposer has been of significant help in reducing the amount of waste. It has been estimated that food waste accounts for approximately sixteen per cent of the household waste.

BRIEF DESCRIPTION OF THE DRAWINGS My invention will be better understood from the following description taken in conjunction with the accompanying drawings and its scope will be pointed out in the appended claims.

FIG. 1 is a front elevational view of an electric incinerator of .the present invention installed in a line of kitchen base cabinets.

FIG. 2 is a right side, cross-sectional elevational view with some parts broken away to show an improved incinerator with a large combustion chamber capable of being sealed by a top access cover that is connected to a front loading door as well as showing the main electric heating means near the front of the housing for reheating the exhaust gases and returning them to the combustion chamber so as to ignite the solid combusti-.

bles therein by means of a recirculating heating system. An afterburner is located beneath this heating compartment.

FIG. 3 is a top, cross-sectional, plan view taken generally along the line 33 of FIG. 2 and looking down into the combustion chamber at the left, and showing a group of four fly ash separators in the form of cyclone separators in the lower right-hand corner of the view, and a preheater mounted directly behind the separators, and finally a single motor supporting on its shaft three blower wheels to provide the proper air flow patterns of primary, secondary, and tertiary air and finally exhaust air from the incinerator. Notice that FIG. 2 is taken on the line 2-2 of FIG. 3 generally through the center line of the combustion chamber.

FIG. 4 is a cross-sectional, elevational view through the back of the incinerator taken on the line 44 of FIG. 3 and showing at the left side the flamebox which extends up from the bottom of the incinerator to the exhaust blower through which the exhaust gases are returned to the atmosphere, as well as showing at the right side of the view a primary air inlet duct for makeup air entering the combustion chamber.

FIG. 5 is a left side, sectional elevational view taken on the line 55 of FIG. 3 showing the cyclone separators at the left, with the elongated preheater mounted directly behind the separators, as well as the motorblower unit in the top corner of the incinerator hous- FIG. 6 is a cross-sectional elevational view taken on the line 66 of FIG. 3 generally through the center of the motor and the first cyclone separator, showing the loading door and access cover in an open position.

FIG. 7 is a block flow diagram showing the main elements of the incinerator system and the various flow patterns for the primary, secondary, and tertiary air streams.

FIG. 8 is a schematic circuit diagram showing the means for controlling the electric heating means and the various control components of the incinerator.

FIG. 9 is a representative time-temperature graph of an incineration cycle of the present invention showing the variation in temperature, as a function of time, of the main heater compartment, the afterburner, the combustion chamber, the bottom wall of the combustion chamber and finally the exhaust temperature.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to a consideration of the drawings, and in particular to FIG. ll, there is shown a domestic incinerator l0 embodying the present invention that is a built-in appliance installed in a base cabinet 15 beneath a kitchen counterop 18, somewhat in the manner of a built-in automatic dishwasher. The incinerator 10 is adapted to be front loaded through a loading door 16 adjacent the top of the incinerator and near the left side thereof. This door 16 is hinged along its bottom edge and it is adapted to be locked by a door handle 17 which may be turned for uncloking the door and gaining access to the interior of the incinerator. It should be understood however that this invention may be employed in a large commercial or industrial size incinerator without departing from the scope of the present invention.

Referring now to the right side, cross-sectional, elevational view of FIG. 2, for a detailed explanation of the structural aspects of the incinerator 10, there is an outer incinerator housing 12 of sheet metal, box-like construction that defines the outer limits of the appliance and forms the supporting structure for the operational components of the incinerator system. It will be appreciated that an incinerator is a high temperature device reaching temperatures above 1,500 F. in some areas, and that thermal insulating means must be provided within the housing 12 to insure that the external surface temperatures of the incinerator do not exceed the regulations of Underwriters Laboratories, Inc., for electric appliances that are to be installed'in a living area such as the kitchen, as distinguished from the basement, the porch or the garage. An air space 11 is formed behind each outer wall of the housing 12 by means of an insulation guard 14 which has associated therewith a layer of theremal insulation 13. This allows for the circulation of cooling room air through the entire air space 11 for restricting the external temperatures of the housing 12. This air space exhausts out through a duct that encircles the exhaust duct 118 of the incinerator.

The incinerator has a combustion chamber formed by an inner liner 22 and a removable, top access cover 24 for loading the combustion chamber with solid waste combustibles through the front-loading door 16. The inner liner 22 has a forwardly inclined semicylindrical front wall 26 as is best seen in FIGS. 2 and 3 with a generally perpendicular, imperforate bottom wall 28, generally parallel side walls 30 and 31, a generally vertical rear wall 33 and a top wall 36 that has a downwardly inclined front portion 37. The removable top cover 24 cooperates with an opening 38 in the inclined top wall 37. Moreover, the removable cover 24 is provided with a sealing gasket 39 which is adapted to be compressed tightly against the peripheral flange of the opening 38 for rendering the combustion chamber 20 generally airtight and preclude the escape of heated gases, smoke, odors, vapors and the like, into the kitchen. A suitable linkage 41 connects the loading door 16 with the access cover 24 such that for each movement of the loading door there is a similar movement of the access cover so that it is not necessary to handle both the door 16 and the cover 24 separately as this would be very inconvenient. Usually the trash would be held in one hand and the loading door 16 would be opened with the other hand and the cover 24 would move simultaneously such that the trash could be inserted through the opening 38 and lowered into the combustion chamber 20.

It has been deemed preferable to locate the incinerator heating means so that it will be in direct contact with the trash or solid combustibles. The heating means could be located within the combustion chamber 20 adjacent the top-of the inner liner 22 and away from the opening 38. However, I have chosen to locate the heating means in the form of an open resistance heating element 4 in a main heater compartment 46 which is positioned at the front of the incinerator housing generally beneath the forwardly inclined semispherical front wall 26 of the inner liner 22. This bare resistance heating element 44 is of wire form, such as nichrome wire, that is supported on a series of ceramic insulators or spools 48 in such a way that it is wound a plurality of turns on each spool and then joined to the adjacent spool 48 and again a plurality of turns are wound on the spool before leading the wire 44 to the next spool. The wattage of this heater wire 44 is about 3000 watts. As shown in the drawing of FIG. 2, there are five insulator spools supporting a nichrome wire before the two heater terminals 50, 51 extend out through insulating bushings 52 in the inner wall 54 that forms the front wall of the main heater chamber 46. This main heating chamber 46 also has a bottom wall 55 and opposite side walls 56, 56 and an inclined semispherical rear wall 57 that is spaced slightly from the inclined, semispherical front wall 26 of the inner liner 22 of the combustion chamber to form a cooling air channel 58 for handling a flow of secondary room ambient air for cooling down the walls of the inner liner 22 as will be more thoroughly explained with relation to the air flow block diagram of FIG. 7. A layer of insulation 59 covers the inner surface of the walls forming the main heating chamber 46.

The combustion chamber 20 is first loaded with solid waste combustibles and the cover 24 is closed and sealed to render the chamber substantially airtight. At the beginning of the cycle, ambient air is precluded from entering the combustion chamber to control the combustion process and vaporize the moisture and other volatiles of the charge of waste. However, when the temperature within the combustion chamber reaches about 800 F. after about 1 to 2 hours, a source of primary air is tapped so that there is a continuous flow of primary air or make-up air in order to support combustion of the waste for the reaminder of the incinerating cycle. Looking at FIG. 2, here is a primary air inlet at 60 comprising a series of three or four small holes arranged horizontally in the back wall 33 of the combustion chamber near the bottom thereof. Behind the back wall 33 is a spaced wall 62 having an air opening 63 adjacent the top thereof. Fastened to this wall 62 is a generally vertical duct 64 having an air inlet opening 65 only at its bottom which is controlled by a bimetal operated damper 67 that is normally closed at temperatures within the combustion chamber below about 800 F. and open thereabove. This temperature is measured by a temperature probe 68 shown mounted against the back wall 33 of the combustion chamber 20 adjacent the'top portion thereof and is part of a logic thermostat 69 found in the schematic circuit diagram of FIG. 8. This thermostat 69 has a normally open switch 70 which is connected in series with a hot wire 71, as well as a normally open switch 72 connected in series with the heating elements 44 and 97 and to be in parallel with the relay switch 75. When the temperature sensed by the thermostat probe 68 of the thermostat 69 reaches about 800 F., the logic thermostat switch 70 will close thereby energizing the hot wire 71 which has a time lag of about 15 minutes after which it closes a normally open bimetal switch 73 thereby energizing a second bimetal actuator 74 that serves to open the damper 67, as well as opening a normally closed bimetal switch 75 in series with the main heater 44 and preheater 97. Simultaneously, the thermostat 69 closes the switch 72 to energize'the heaters 445 and 97, thereby placing these heaters under the control of the logic thermostat 69.

As the primary air is introduced into the combustion chamber 20 after the damper 67 has been opened, it will be drawn into a blower 77 located in the upper portion of the right side wall 31 of the combustion chamber 20 as is best seen in FIGS. 2 and 3. This blower 77 has a blower wheel 78 mounted on the shaft 79 of an electric motor 80. This same motor shaft 79 also carries a second blower wheel 81 and an exhaust blower wheel 82 for reasons which will be explained hereinafter. The first blower wheel 78 is mounted in a split scroll 84 which has two discharge openings; namely, a downwardly inclined discharge opening at 85 within the combustion chamber 20, as seen in FIG. 2, and a generally horizontal discharge duct 86 which leads out through an opening in the side wall 31 of the inner liner 22 of the combustion chamber 20 and discharges into a fly ash separator in the form of a series of four cyclone separators. The first cyclone separator 88 is seen in plan view in FIG. 2. The first discharge duct 85 is for sending a blast of air down into the combustion chamber at a high velocity so that the air is able to reach the many isolated air pockets within the solid combustibles and to support the combustion thereof. Hence, there is an air stream from the combustion chamber 20 drawn into an air inlet opening 89 in the side of the scroll 84 of the first blower 77. One part of this air stream is divided out to return to the combustion chamber through the vertical air duct 85, and the remaining part of the air stream is led off through the horizontal duct 86 to pass into the first cyclone separator 88.

It is important to separate the fly ash from the flue gases as they exit from the combustion chamber 20 through the discharge duct 86. Rather than provide a single fly ash separator, I have elected to adopt a more efficient system of a grouping of four cyclone separators, each of generally standard design characteristics, and each with its own removable ash collector at the bottom, such as the quart jar 91 shown in FIG. 5. Looking at FIG. 3, there are two fly ash separators 88 and 92 of about equal size, and they are connected in series, and then there are two smaller separators 93 and 94 which are arranged in parallel and are both connected directly to the exhaust of the second separator 92. As an example, for every pounds of solid waste combustibles consumed in the combustion chamber there would be about four ounces of fly ash in the various removable jars 911 that are mounted on the bottom of each separator 88, 92, 93 and 94.

Understandably, there would have to be a small access door 120 built into the front wall 12 of the incinerator housing in the vicinity of the lower portion of the four fly ash separators 88, 92, 93 and 94 so that access could be gained to the removable fly ash collectors or jars 92 mounted on the bottom of each separator. Then the fly ash may be emptied periodically and the container replaced for future use. A suitable handle 121 could be located adjacent the top edge for locking the door in place and for opening it.

Turning attention to the gas flow block diagram of FIG. 7, the gas passes from the fly ash separator 87 to a preheater unit 96 which is vertically mounted just behind the fly ash separator, as is best seen in FIGS. 3 and 5. The purpose of this preheater unit is to raise the temperature of the gas to a maximum of about 1,100 F. before the gas is delivered to the main heater chamber 46 where the gas is heated further to a maximum of about l,500 F. and most of the smoke, odors and vapors are comsumed. The preheater unit 96 is supplied with a plurality of metal sheathed resistance heating elements 97, shown as four in number as in FIG. 5, which are of serpentine configuration and extend almost the entire height of the incinerator housing so that the gas is exposed to these heaters 97 for as long a time as possible as the gas passes down the unit and exits through an opening 93 adjacent the bottom of the preheater which is in communication with the main heater chamber 46, as is best seen in FIG. 2. The total preheater wattage is about 3,000 watts. This degree of temperature of 1,500 P. would be damaging to most metal sheathed resistance heating elements. Hence, the heaters 44 of the main heater 416 are of bare resistance heater wire wound on the insulating spools 48 as described heretofore.

From the main heater chamber 46, the gas is returned to the combustion chamber 20 through the upper opening 100 shown in FIG. 2 where the heated gas is drawn into the first blower means 77 and is separated by the split scroll 84 such that part of the gas is blasted down into the combustion chamber through the duct and the remainder is exhausted from the combustion chamber through the exhaust duct 86 to the fly ash separator 87. Thus, it will be understood that gas is recirculated within the combustion chamber 20 through the first blower 77 and the air duct 85, while there is a second recirculation system for the combustion chamber as is best understood from the block diagram of FIG. 7 comprising the exhaust duct 36, the fly ash separator 97, the preheater unit 96 and the main heater unit 46. The air flowing back through the combustion chamber to continue this recycling action for removing as much of the fly ash from the flue gases as is possible and consuming the smoke, odors, vapors and volatiles entrained therein and reheating the air for the ignition of the solid waste combustibles.

It will be understood by those skilled in this art that it is technically feasible to combine the preheater unit 96 with the main heater 46 in order to raise the temperature of the gases in one step as they pass from the fly ash separator 87 and are returned to the combustion chamber 20. As a practical matter, this is a function of temperature of the heating means and time that the gases are exposed to the heaters before they are returned to the combustion chamber 20. The combination of the preheater and the main heater is preferred to enable the use of metal sheathed heaters at the lower temperatures experienced within the preheater. It will also be understood that during the initial phase of the combustion cycle when the primary air inlet damper 67 is closed, that most of the oxygen present in the air and gases existing within the sealed combustion chamber is consumed by the ignition of the combustibles and is not replenished during the recylcing through the fly ash separator, preheater and main heater and back to the combustion chamber. This oxygen starved condition served to control the combustion process and prevent backfires as the volatiles within the solid combustibles are driven off. Primary air is allowed to enter the combustion chamber only after the temperature within the combustion chamber reaches about 800 F. as sensed by the temperature probe 68 arranged adjacent the back wall 33 of the inner liner 22.

Again looking at the block diagram of FIG. 7, it will he noticed that an afterburner 102 is located downstream of the main heater 46 so that all of the gases passing through the main heater chambef 46 are not returned to the combustion chamber 20. A small amount of the gases is passed to the afterburner 102 by way of a triangular shaped, vertical duct 104 shown along the left side of the plan view of FIG. 3, which empties down into the afterburner 102 that is located beneath the main heater chamber 46, as is best seen in FIG. 2. A layer of insulation 103 covers the walls forming the afterburner chamber 102. Since there is a reduced amount of oxygen in the gases discharging from the main heater chamber 46, a supply of secondary air is provided for the afterburner 102 so as to oxidize the combustibles that might still remain in the flue gases. This secondary air is brought into the incinerator housing by means of the second blower wheel 81 shown in FIGS. 3 and 6. Leading from the scroll 83 around this second blower wheel 81 is an inclined exhaust duct 106 which enters the air channel 58 shown in FIG. 2 through an opening 107 in the wall 57 that parallels the front wall 26 of the inner liner 22. This secondary air is in contact with the semicylindrical front wall 26 of the inner liner 22 for cooling down the walls of the combustion chamber as well as for preheating the secondary air before it enters the afterburner 102 as through a lower opening 109 shown in' FIG. 2.

Looking at the rear view of the incinerator of FIG. 4, you will notice the upper and lower fragments of an inclined secondary air duct 111 which has an intake opening 112 near the floor and which has an upper opening adjacent the motor 80 so that room ambient air is first drawn over the motor for cooling the windings thereof before being drawn into the blower opening 112 of the second blower wheel 81 as is best seen in FIG. 3. Thus, the function of the secondary air is to cool the windings of the motor 80 as well as to cool down the walls of the combustion chamber 20 by passing secondary air through the air chamber 58, and then to supply oxygen to the afterburner 102 for oxidizing the conbustibles in the flue gases after they exit from the main heater chamber 46 when the gases become separated from the recirculating cycle.

The third blower wheel 82 is part of an exhaust means which is arranged downstream of the afterburner 102. But first, it is well to insure that there are no combustibles in the flue gases exhausting from the afterburner that might reach the blower wheel 82. This assurance is provided by a flamebox 113 that is generally an elongated box-like construction formed up the back side of the incinerator housing generally behind the preheater 96 and beneath the motor 80 and blower units as is best seen in FIG. 4. A lower opening 115 connecting the afterburner 102 to the flamebox 113 is shown in FIG. 5.

It is also desirable to provide a source of room air or tertiary air for the flamebox. A tertiary air inlet opening 116 is located in the front wall of the flamebox as is shown in FIG. 5. This tertiary air is drawn into the flamebox by means of the exhaust blower 82 to further oxidize the combustibles in the flue gases and insure that the gases are free of all smoke, odors, vapors and volatiles before the gases are returned to the outside atmosphere. Leading from the exhaust blower 82 is an exhaust duct 118 that protrudes slightly beyond the back wall of the incinerator housing 10 and is adapted to be coupled to a vent system (not shown) extending through a kitchen wall or alternately up through the wall to the roof when the incinerator 10 is slid back into place beneath the kitchen counter 14.

Most of the structural elements of this incinerator design have been described above in some detail. Attention will now be given to the circuit diagram of FIG. 8. This incinerator model is provided with a three-wire electrical service nominally of 240 volts, single phase, 60 cycle A.C. which is usually available in the average residence having adequate wiring. This voltage source has a pair of line wires L, and L and a grounded neutral conductor N, there being 120 volts measured between either line L, or L and netural N, and 240 volts measured between the two line wires L, and L The preheater 97 and the main heater 44 are connected in series across lines L, and L at 240 volts by means of leads 160 and 162.

A first door interlock switch 132 is connected in lead 160, and a second door interlock switch 133 is connected in lead 180. These two normally open switches are connected together to act in unison. When the incinerator loading door 16 is closed and locked, the two door interlock switches will be closed. The incinerator loading door 16 has a door lock 17, with the lock mechanism not shown, but its function is to insure that the incinerator 'cycle cannot be initiated unless the door 16 is first closed and locked. The lock mechanism cooperates with the door interlock switches 132 and 133 to close these switched when the door is fully locked. Once the incinerator temperature rises above about 350 F. the door interlock thermostat 12S operates to de-energize a door latching solenoid such that it is not possible to unlock the door when the temperature within the combustion chamber is above 350 F. This type of door lock system would be similar to that taught in the Getman Reissue U.S. Pat. No. 26,944, which is assigned to the same assignee as is the present invention. The door lock mechanism 17 has an automatic locking bolt 164 shown diagrammatically in FIG. 8. This automatic locking bolt is a pivoted, spring biased member that automatically engages within the leeper 116 of a rod 167 of the door lock mechanism when it is in the closed position. This locking bolt 164 is acted upon by a solenoid 129 which is adapted to be energized across line L, and neutral lead N by lead 169 through a momentary contact switch 130 in series therewith and by lead 171 through a normally closed switch 131 of a door interlock thermostat 125. This thermostat is set to operate when the temperature within the combustion chamber rises above about 350 F. This causes the switch 131 to stay open, thereby deactivating the solenoid 129 such that the door lock 17 and its rod 167 cannot be released from the automatic locking bolt 164. The indicator lights 136 and 137 are connected across line L, and neutral line N such that the first indicator light 136 indicates when it is possible to open the load door 16 and the second indicator light 137 operates alternately with the first light such that is indicates when the temperature in the combustion chamber is above 350 F. at which time it is not possible to unlock and open the door 16. This lighting arrangement is obtained by connectong the first indicator light 136 or OPEN light to line L, by means of lead 138 and to be in series with the thermostat switch 131 by means of lead 139 connected to lead 171, such that this OPEN light 136 is energized whenever the door interlock thermostat switch 131 is in its normally closed position at temperatures below 350 F. The second indicator light 137 or LOCKED light is connected to line L, by means of lead 140 and by lead 142 to be in series with a normally open switch 141 of the door interlock thermostat 125 such that at a temperature above about 350 F. after the door interlock thermostat functions the thermostat switch 141 will close thereby completing the circuit through the LOCKED light 137 to indi cate that it is no longer possible to unlock the incinerator door until the temperature within the combustion chamber drops below the critical temperature of about 350 F.

The blower motor 80 is arranged to be connected in parallel with the LOCKED light 137 and to be in series with the thermostat switch 141 of the door interlock thermostat 125 such that the motor 80 is energized after the door interlock thermostat 125 operates at its critical temperature of about 350 F. The motor 80 is connected to line L, by lead 143 and to the thermostat switch 141 by means of lead 144 connected to lead 142.

An agitator 146 is shown mounted in the bottom of the inner liner 22. This agitator is driven by a geareddown motor 147 which is connected in parallel to work in unison with the blower motor 80 by means of lead 149 and lead 150 that is connected with lead 144.

There is an overtemperature protective thermostat 165 connected in lead 160 in series with the preheater 97 and main heater 44. This thermostat is normally closed and it opens when the temperature within the main heater compartment 46 reaches about l,5() F. The temperature probe for this thermostat 165 is shown in FIGS. 2 and 3 as element 153 and located in a generally vertical position adjacent the insulated curved wall 57 that surrounds the front wall of the inner liner 22. This protects the incinerator from runaway conditions and de-energizes the heating elements whenever the tmeperature within the main heater compartment becomes excessive.

The third-thermostat, a logic thermostat 69, which had been mentioned previously, is utilized to control the primary air damper 67 that is located at the inlet of the primary air duct 64. The opening of the damper 67 is controlled by a bimetal actuator 74 that is connected in series with a normally open switch 73 of a bimetal relay 175 to be connected across line L, and neutral N by lead 177 and lead 178 that is in turn connected in series with the normally open switch 141 of the door interlock thermostat 125. The relay 175 also has a normally closed switch 75 that is connected in series with the preheater 97 and the main heater 44 by lead 162, and connects these heaters at high voltage across lines L, and L by lead 180. The operation of the relay 175 is controlled by the logic thermostat 69. As mentioned previously, the logic thermostat 69 is calibrated to operate at a temperature within the combustion chamber of about 800 F. When it does trip it energizes the bimetal 71 of the relay 175. This bimetal heater 71 has a delay time of about 15 minutes after which it actuates the two bimetal switches 73 and 75 to connect the damper bimetal heater 74 directly across line L, and neutral N.

The logic thermostat 69 has a pair of normally open switches 70 and 72. Switch 72 was described above.

Switch is connected in series with the door interlock switch 132 and line L, by leads 136 and 160, and joined to the hot wire 71 of the relay 175 by lead 188. A solidstate rectifier or diode 190 is arranged in lead 188 to pass current only between the switch 70 and the hot wire 71. Likewise a second diode 192 is arranged in a lead 194 to pass current in-a direction from a point 196 in between the bimetal switch 73 and the damper bimetal 74 with a point 198 in lead 188 between the diode 190 and the hot wire 71. These diodes 138 and 192 serve to prevent feedback circuits through the logic thermostat 69. The normally closed contact on bimetal supplies power to heaters 97 and 44 through leads 160, 162 and 180 between lines L, and L It now opens and will remain open for the remainder of the incineration cycle due to heat from bimetal heater 71 that stays energized through the simultaneous closing of normally open contact on bimetal 73 and lead 194 through rectifier 192 connected at points 196 and 198. The heater '71 will not lose this energy before interlock thermostat contacts 141 open. It should be noted that contact 72 of logic thermostat 69 closes well before the contact 75 in the bimetal relay 175 opens so as to transfer the circuit for the two heaters 97 and 44 through leads 182 and 184. This condition continues until the sensor 68 of FIGS. 2 and 3 of the logic thermostat 69 senses a temperature well below 800 F. thereby causing contacts 70 and 72 to open. At the opening of contact 72 the power to heaters 97 and 44 is interrupted and the combustion chamber 20 will cooldown until the door interlock sensor 127 shown in FIG. 3 is below about 300 F. at which time switch 141 opens in the door interlock switch 125, and the power to the blower motor and agitator motor 147 and door LOCKED light 137 is interrupted.

Looking at the temperature curves of FIG. 9, it is clear that an average operating cycle'is between 2 and 3 hours. The first curve A is the temperature within the main heater chamber 46 with a maximum temperature of about 1,500 F. The second curve B is the temperature within the afterburner chamber 102 and it takes longer to reach its maximum temperatre and its temperature drops off quicker than that of curve A. The third curve C shows the temperature variations of the combustion chamber 20 as experienced by the sensor 153 of the overtemperature protective thermostat 165. The fourth curve D indicates the temperature of the bottom wall 28 of the combustion chamber 20 which is very slow to reach its maximum temperature indicating that much of the burning action takes place toward the top of the load of waste within the combustion chamber and works its way downward. The last curve B indicates the relatively cool nature of the incinerator exhaust.

Modifications of this invention will occur to those skilled in this art, therefore, it is to be understood that this invention is not limited to the particular embodiments disclosed, but that it is intended to cover all modifications which are within the true spirit and scope of this invention as claimed.

What is claimed as new and desired to be secured by Letters Patent of the United Stats is:.

1. An incinerator comprising a housing enclosing a combustion chamber, an access cover for loading the chamber with solid combustibles, and means for sealing the cover during the operating cycle, heating means external of the chamber, primary air inlet means to the chamber, a first blower means associated with the chamber for both recirculating a blast of air within the chamber and for discharging a portion of the air from the chamber to a fly ash separator means, and a preheater means for receiving the air discharged from the separator means and raising the temperature tereof, the air passing from the preheater means to the said external heating means and then re-entering the combustion chamber at a high temperature to ignite the solid combustibles, an afterburner means associated with the external heating means for receiving some of the discharge from the said heating means, flamebox means downstream of the afterburner to complete the combustion of any volatiles that might remain in the air, and an exhaust blower means associated with the flamebox for discharging the air stream to the atmosphere.

2. An incinerator as recited in claim 1 with a third blower means for passing a stream of secondary air over a portion of the walls forming the combustion chamber, said secondary air being introduced to the said afterburner to assist in supporting combustion and oxidizing the combustibles in the air stream entering from the external heating means;

3. An incinerator as recited in claim 2 with an ambient air inlet means to the flamebox for introducing a supply of tertiary air to further oxidize the combustibles therein and extinguish all flames before the air stream is drawn through the said exhaust blower means.

4. An incinerator comprising an outer housing enclosing a combustion chamber formed by a drum-like container with a removable cover for loading the container with solid combustibles, means for sealing the cover to the container during the operating cycle, heating means external of the chamber, primary air inlet means into the chamber, double blower means associated with the chamber for directing a blast of primary air back into the combustion chamber as well as for discharging a portion of the primary air from the chamber, a fly ash separator means downstream of the discharge of the double blower means, the said heating means being downstream of the fly ash separator means for raising the temperature of the air, an air reentry means from the heating means to the combustion chamber for igniting the solid combustibles in a closed heating cycle, and an afterburner associated with the heating means for bleeding off a portion of the air from the heating means, and a second blower means for passing a stream of secondary air around a portion of the incinerator combustion chamber for restricting the maximum temperature thereof, said secondary air being introduced to the afterburner for oxidizing the combustibles in the exhaust gases passing therethrough, and an exhaust means from the afterburner to the atmosphere.

5. An incinerator as recited in claim 4 with a preheater means interposed between the fly ash separator means and the heating means for assisting in raising the temperature of the exhaust gases before they are returned to the combustion chamber.

6. An incinerator as recited in claim 4 with a flamebox interposed downstream of the afterburner, and an ambient air inlet means in the flamebox to introduce tertiary air to further oxidize the combustibles in the flamebox and extinguish all flames, and an exhaust blower means downstream of the flamebox for exhausting the flamebox to the atmosphere.

7. An incinerator for solid combustibles comprising an outer box-like housing enclosing a combustion chamber formed by an inner liner and a top-opening access cover, sealing means for rendering the cover substantially airtight, air heating means external of the inner liner for heating the outflow from the combustion chamber and returning it to the combustion chamber for igniting the solid combustible load, a controlled primary air inlet means in the combustion chamber including a normally closed temperature-responsive damper at inner combustion chamber temoeratures below a temperature somewhere between 600 F. and 900 F. so that the initial operation of the incinerator is in an oxygen-starved condition so as to have controlled combustion and avoid backflres.

8. An incinerator for solid conbustibles as recited in claim 7 with a recirculating blower means associated with the combustion chamber for circulating a blast of primary air within the combustion chamber.

9. An incinerator for solid combustibles as recited in claim 8 wherein the said recirculating blower means also has a partial discharge of the primary air representing the said outflow from the combustion chamber, a fly ash separator means for receiving this outflow, the said air heating means being downstream of the fly ash separator means for receiving the discharge thererom, and an afterburner downstream of the air heating means for receiving a portion of the air flow therefrom, and a second blower means associated with the afterburner for introducing secondary air into the afterburner for oxidizing the gaseous combustibles in the primary air passing therethrough, and an exhaust means from the afterburner to the atmosphere.

10. An incinerator for solid combustibles as recited in claim 9 wherein the said exhaust means includes a flamebox downstream of the afterburner for receiving the discharge thererom, and a third blower means associated with the flamebox for introducing tertiary air into the flamebox and completing the combustion of any volatiles in the air before it passes back into the atmosphere.

11. An incinerator for solid combustibles as recited in claim 10 wherein the said three blower means are driven by a single motor drive.

12. A domestic incinerator for solid combustibles comprising an outer box-like housing enclosing a combustion chamber formed by an inner liner and a topopening access cover, sealing means for rendering the cover substantially airtight, a controlled primary air inlet means for the combustion chamber including a temperature responsive damper that is normally closed at inner combustion chamber temperatures below about 600 F. sothat the initial operation of the incinerator is in an oxygen-starved condition so as to have controlled combustion and avoid backfires, a first blower means downstream of the air inlet means for recirculating a blast of air within the combustion chamber, said blower means also discharging a portion of the air from within the combustion chamber, a fly ash separator downstream of this blower discharge, an electric heating means downstream of the fly ash separator for raising the temperature of the air above about l,400 F., and hot air return means from the heating means to the combustion chamber for igniting the solid combustibles therein, and an afterburner means associated with the heating means for receiving a portion of the air flow through the heating means, and a second blower means for passing a stream of secondary air over a portion of the combustion chamber for restricting the maximum external temperatures of the housing, said secondary air then being introduced into the afterburner means for oxidizing the combustibles in the primary air passing therethrough, and a third suction blower means downstream of the afterburner means for exhausting the products of combustion to the atmosphere.

13. A domestic incinerator for solid combustibles as recited in claim 12 with a flamebox interposed between the afterburner means and the suction blower means, and an ambient air inlet opening in the flamebox for introducing tertiary air into the flamebox to further oxiblower means have a common drive means.- 

1. An incinerator comprising a housing enclosing a combustion chamber, an access cover for loading the chamber with solid combustibles, and means for sealing the cover during the operating cycle, heating means external of the chamber, primary air inlet means to the chamber, a first blower means associated with the chamber for both recirculating a blast of air within the chamber and for discharging a portion of the air from the chamber to a fly ash separator means, and a preheater means for receiving the air discharged from the separator means and raising the thereof, tereof, the air passing from the preheater means to the said external heating means and then re-entering the combustion chamber at a high temperature to ignite the solid combustibles, an afterburner means associated with the external heating means for receiving some of the discharge from the said heating means, flamebox means downstream of the afterburner to complete the combustion of any volatiles that might remain in the air, and an exhaust blower means associated with the flamebox for discharging the air stream to the atmosphere.
 2. An incinerator as recited in claim 1 with a third blower means for passing a stream of secondary air over a portion of the walls forming the combustion chamber, said secondary air being introduced to the said afterburner to assist in supporting combustion and oxidizing the combustibles in the air stream entering from the external heating means.
 3. An incinerator as recited in claim 2 with an ambient air inlet means to the flamebox for introducing a supply of tertiary air to further oxidize the combustibles therein and extinguish all flames before the air stream is drawn through the said exhaust blower means.
 4. An incinerator comprising an outer housing enclosing a combustion chamber formed by a drum-like container with a removable cover for loading the container with solid combustibles, means for sealing the cover to the container during the operating cycle, heating means external of the chamber, primary air inlet means into the chamber, double blower means associated with the chamber for directing a blast of primary air back into the combustion chamber as well as for discharging a portion of the primary air from the chamber, a fly ash separator means downstream of the discharge of the double blower means, the said heating means being downstream of the fly ash separator means for raising the temperature of the air, an air reentry means from the heating means to the combustion chamber for igniting the solid combustibles in a closed heating cycle, and an afterburner associated with the heating means for bleeding off a portion of the air from the heating means, and a second blower means for passing a stream of secondary air around a portion of the incinerator combustion chamber for restricting the maximum temperature thereof, said secondary air being introduced to the afterburner for oxidizing the combustibles in the exhaust gases passing therethrough, and an exhaust means from the afterburner to the atmosphere.
 5. An incinerator as recited in Claim 4 with a preheater means interposed between the fly ash separator means and the heating means for assisting in raising the temperature of the exhaust gases before they are returned to the combustion chamber.
 6. An incinerator as recited in claim 4 with a flamebox interposed downstream of the afterburner, and an ambient air inlet means in the flamebox to introduce tertiary air to further oxidize the combustibles in the flamebox and extinguish all flames, and an exhaust blower means downstream of the flamebox for exhausting the flamebox to the atmosphere.
 7. An incinerator for solid combustibles comprising an outer box-like housing enclosing a combustion chamber formed by an inner liner and a top-opening access cover, sealing means for rendering the cover substantially airtight, air heating means external of the inner liner for heating the outflow from the combustion chamber and returning it to the combustion chamber for igniting the solid combustible load, a controlled primary air inlet means in the combustion chamber including a normally closed temperature-responsive damper at inner combustion chamber temperatures below a temperature somewhere between 600* F. and 900* F. so that the initial operation of the incinerator is in an oxygen-starved condition so as to have controlled combustion and avoid backfires.
 8. An incinerator for solid conbustibles as recited in claim 7 with a recirculating blower means associated with the combustion chamber for circulating a blast of primary air within the combustion chamber.
 9. An incinerator for solid combustibles as recited in claim 8 wherein the said recirculating blower means also has a partial discharge of the primary air representing the said outflow from the combustion chamber, a fly ash separator means for receiving this outflow, the said air heating means being downstream of the fly ash separator means for receiving the discharge therefrom, and an afterburner downstream of the air heating means for receiving a portion of the air flow therefrom, and a second blower means associated with the afterburner for introducing secondary air into the afterburner for oxidizing the gaseous combustibles in the primary air passing therethrough, and an exhaust means from the afterburner to the atmosphere.
 10. An incinerator for solid combustibles as recited in claim 9 wherein the said exhaust means includes a flamebox downstream of the afterburner for receiving the discharge therefrom, and a third blower means associated with the flamebox for introducing tertiary air into the flamebox and completing the combustion of any volatiles in the air before it passes back into the atmosphere.
 11. An incinerator for solid combustibles as recited in claim 10 wherein the said three blower means are driven by a single motor drive.
 12. A domestic incinerator for solid combustibles comprising an outer box-like housing enclosing a combustion chamber formed by an inner liner and a top-opening access cover, sealing means for rendering the cover substantially airtight, a controlled primary air inlet means for the combustion chamber including a temperature responsive damper that is normally closed at inner combustion chamber temperatures below about 600* F. so that the initial operation of the incinerator is in an oxygen-starved condition so as to have controlled combustion and avoid backfires, a first blower means downstream of the air inlet means for recirculating a blast of air within the combustion chamber, said blower means also discharging a portion of the air from within the combustion chamber, a fly ash separator downstream of this blower discharge, an electric heating means downstream of the fly ash separator for raising the temperature of the air above about 1,400* F., and hot air return means from the heating means to the combustion chamber for igniting the solid combustibles therein, and an afterburner means associated with the heating means for receiving a portion of the air flow thRough the heating means, and a second blower means for passing a stream of secondary air over a portion of the combustion chamber for restricting the maximum external temperatures of the housing, said secondary air then being introduced into the afterburner means for oxidizing the combustibles in the primary air passing therethrough, and a third suction blower means downstream of the afterburner means for exhausting the products of combustion to the atmosphere.
 13. A domestic incinerator for solid combustibles as recited in claim 12 with a flamebox interposed between the afterburner means and the suction blower means, and an ambient air inlet opening in the flamebox for introducing tertiary air into the flamebox to further oxidize the combustibles in the air therein, as well as to extinguish all flames and cool down the exhaust.
 14. A domestic incinerator for solid combustibles as recited in claim 13 with an electric preheater means interposed between the fly ash separator and the said heating means for raising the temperature of the air discharging from the fly ash separator means to about 1,000* F. before it passes onto the main heating means.
 15. A domestic electric incinerator for solid combustibles as recited in claim 14 wherein the said three blower means have a common drive means. 